I. Field of the Invention
The present invention relates to apparatus for the detection of bearing and other malfunctions in machinery. More specifically, the present invention relates to portable vibration monitors and vibration coupling studs for monitoring the vibrational and other characteristics of the machine.
II. Description of the Related Art
In order to properly maintain machinery used in manufacturing facilities, power generating stations, etc., it has become common to employ vibration monitoring equipment to detect variations in the vibration characteristics of the machinery while they are operating. This assists in the determination of appropriate intervals for machine maintenance, and as a warning of imminent machine failure. It can be appreciated that proper scheduling of maintenance can improve the operating efficiency of the facility, and that a warning of imminent machine failure can avoid catastrophic machine damage as well as danger to facility personnel.
Many systems have been developed to implement such a monitoring procedure. In some systems, as described in U.S. Pat. No. 5,430,663 to Judd et al., for example, transducers are fixed to machinery throughout a plant or other facility, and the electrical signals from the transducers are wired to a central computer system for monitoring. Another system of this nature is described in U.S. Pat. No. 5,191,327 to Talmadge et al. In the system described by Talmadge, the analog transducer signal is pre-processed with programmable filtering circuitry located within the transducer housing. The central computer of the Talmadge et al. system can both store and retrieve transducer ID data and instructions directing signal pre-processing into and out of a memory located within the transducer housing at the measuring point.
Systems of this design have the advantage that all points of interest in the plant can be continuously and simultaneously monitored. However, such a system is expensive to implement, requiring a large number of dedicated vibration transducers as well as interconnecting wiring strung throughout the facility. Accordingly, such implementations are most useful in situations where machine failure may have especially serious consequences, such as in a nuclear power plant for example.
A less expensive alternative to such a system uses a portable monitoring probe having an internal trasducer and signal processing circuitry. A system such as this is described in U.S. Pat. No. 4,520,674 to Canada et al. In systems of this design, plant personnel will walk a generally predetermined route around a facility being monitored in order to apply a portable data collection device to measuring points at various locations on the machinery to be monitored. In the Canada et al. patent, for example, a technician carries a handheld probe which is connected to a separate portable data collection and processing device. One portion of the handheld probe is placed either in direct contact with the outside of the machine to be monitored, or in direct contact with a vibration coupling stud secured to the outside of the machine to be monitored. Mechanical vibration is thus coupled to an internal piezoelectric vibration transducer for creating an electrical signal indicative of the vibratory acceleration of the machine being monitored. The handheld probe then outputs an analog vibration signal to a separate data collection and processing device. Vibration parameters such as acceleration and velocity are calculated and stored for later analysis.
A commercially available device of this nature is the Picolog (TM) from SKF Condition Monitoring of San Diego, Calif. The Picolog system comprises a handheld probe capable of measuring and storing hundreds of separate vibration level measurements. These measurements are later uploaded to a host computer system for analysis. The Picolog (TM), however, does not provide a real-time output of the vibration measurement.
Although these systems are relatively inexpensive, they have several disadvantages. One fundamental disadvantage is that the technician must accurately record where and when each vibration measurement is taken. Although a specific route which is followed by all technicians when gathering vibration data may be established, but this increases the required training, and some transcriptional or other route errors are essentially inevitable.
Although some devices have been designed to alleviate this problem, significant potential for improvement remains. A system described in U.S. Pat. No. 4,800,512 to Busch discloses a vibration data measuring probe which can read a measuring point code from a vibration coupling stud located at a particular measuring point. The coupling stud of this system includes a unique identifier such as a bar code, a specific arrangement of magnets, a ridge pattern, or other similar identifying characteristic. When the portable probe is applied to the coupling stud, a reader slides along the bar code, magnets, ridges, etc., thereby creating a signal which is transferred to a computer attached to the probe. This system is stated to allow the computer to identify the coupling stud the probe is attached to, thereby reducing or eliminating the need to manually transcribe information regarding the data point. However, the amount of information storable in the vibration coupling stud is very limited, and the probe required to read the code is mechanically complex.
What is needed in the art is therefore a vibration data collection system which incorporates increased capabilities for data storage at the measuring point, which is easy to use, and which is inexpensive to manufacture.